ABCD is a quadrilateral with AB horizontal and CD vertical. Angle BAD = angle BCD = 40 degrees and AB=BC=5. Show that angle CDB = angle ADB = 25 degrees.
Here is a diagram I made which I hope is correct:
By observing alternate angles, I can see that angle ADC = 50 degrees but how do I show that angle CDB = angle ADB? I thought about proving congruence but is this possible here?